Global positioning system (GPS) technology or any other satellite-based position technology provide mobile devices, such as mobile phones, a method to determine the position thereof by triangulation. Assisted-GPS provides a faster positioning technology by a priori determining which satellites to listen to.
A disadvantage with satellite-based position technologies, is that they are not as such well suited for in-door or under-a-roof positioning applications, as multiple reflections make the received signals less reliable.
Uplink time difference of arrival (UTDOA) is an alternative technology that determines the position of a transmitter by measuring the difference in time of arrival of a signal transmitted by the transmitter in three or more receivers. The difference in time of arrival of the signal depends on the difference in distance between the transmitter and the different receivers. UTDOA depends on thermal stability of clocking oscillators, synchronization of the transmitter oscillator with the receiver oscillators, as well as phase synchronization of the transmitted signal with the received signal(s).
In a WIFI environment a mobile phone may use local WIFI routers to locate itself. This however requires information about where the WIFI routers themselves are placed.
In-building-solutions are specialized solutions to create capacity and coverage for mobile communication indoors by using a dedicated indoor network for mobile communication. These networks typically consist of a distributed antenna system where one large radio base station is connected to a network of small indoor antennas inside the building. Needless to say, this system requires installations of a distributed antenna system.
There is hence a need to provide positioning of communication devices either inside buildings, without the need to actively install software in or to configure said communication devices in any way, or to provide positioning out-doors in a facilitated manner. This is beneficial where satellite-based navigation is not possible due to low signal reliability or when GPS and/or WiFi are turned off to save battery.
There is also a demand for positioning arrangements that can be quickly set up and work even without working communication infrastructure to passively provide positioning of communication devices, such as mobile phones or vehicles with such means, in order to facilitate location of people in need in case of disasters or accidents.